Carriage for ink-jet hard copy apparatus

ABSTRACT

A carriage for an ink-jet printer constrains torsional deflections by providing carriage to writing-instrument latch interface features having a zero clearance interfit such that when opened, the writing-instrument latch allows individual writing-instruments to be accessed and when closed the writing-instrument latch reduces the carriage torsional deflections and increases the torsional stiffness of the carriage by providing a biasing force at each the interface feature.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to ink-jet printing and, morespecifically to an ink-jet pen carriage assembly having a torsionaldeflection control pen latching subsystem for increasing stiffness andmaintaining accurate pen-to-paper alignment.

2. Description of Related Art

The art of ink-jet technology is relatively well developed. Commercialproducts such as computer printers, graphics plotters, copiers, andfacsimile machines employ ink-jet technology for producing hard copy.The basics of this technology are disclosed, for example, in variousarticles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985), Vol.39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4(August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No. 1(February 1994) editions. Ink-jet devices are also described by W. J.Lloyd and H. T. Taub in Output Hardcopy [sic] Devices, chapter 13 (Ed.R. C. Durbeck and S. Sherr, Academic Press, San Diego, 1988).

FIG. 1 depicts a hard copy apparatus, in this exemplary embodiment acomputer peripheral, ink-jet printer, 101. A housing 103 encloses theelectrical and mechanical operating mechanisms of the printer 101.Operation is administrated by an electronic controller 102 (usually amicroprocessor or application specific integrated circuit (“ASIC”)controlled printed circuit board) connected by appropriate cabling to acomputer (not shown). It is well known to program and execute imaging,printing, print media handling, control functions and logic withfirmware or software instructions for conventional or general purposemicroprocessors or with ASIC's. Cut-sheet print media 105, loaded by theend-user onto an input tray 120, is fed by a suitable paper-pathtransport mechanism (not shown) to an internal printing station, or“print zone,” 107 where graphical images or alphanumeric text iscreated. A carriage 109, mounted on a slider 111, scans the printmedium. [Stationary, page-wide, ink-jet printhead arrays are also knownin the art; page-size printhead arrays are contemplated.] An encodersubsystem 113, 114 is provided for keeping track of the position of thecarriage 109 at any given time. A set of individual ink-jet pens, orprint cartridges, 115X is mounted in the carriage 109 (described in moredetail hereinafter with respect to FIG. 2B). Generally, in a full colorsystem, inks for the subtractive primary colors, cyan, yellow, magenta(X=C, Y, or M) and true black (X=K) are provided; in someimplementations an ink-fixer chemical (X=F) is also used. An associatedset of replaceable or refillable ink reservoirs 117X is coupled to thepen set by ink conduits 119. Once a printed page is completed, the printmedium is ejected onto an output tray 121. The carriage scanning axis isconventionally designated the x-axis, the print media transit axis isdesignated the y-axis, and the printhead firing direction is designatedthe z-axis.

For convenience of describing the ink-jet technology and the presentinvention, all types of print media are referred to simply as “paper,”all compositions of colorants are referred to simply as “ink,” ink-jetwriting instruments are referred to as “pens” or “cartridges,” and alltypes of hard copy apparatus are referred to simply as a “printer.” Nolimitation on the scope of invention is intended nor should any beimplied.

In essence, the ink-jet printing process involves digitized dot-matrixmanipulation of drops of ink ejected from an ink-jet printhead onto anadjacent paper. The printhead generally consists of drop generatormechanisms and a number of columns of ink drop firing nozzles. Eachcolumn or selected subset (referred to in the art as a “primitive”) ofnozzles selectively fires ink droplets (typically each being only a fewpicoliters in liquid volume) that are used to create a predeterminedprint matrix of dots on the adjacently positioned paper as the pen isscanned across the media. A given nozzle of the printhead is used toaddress a given matrix column print position on the paper (referred toas a picture element, or “pixel”). Horizontal positions, matrix pixelrows, on the paper are addressed by repeatedly firing a given nozzle atmatrix row print positions as the pen is scanned. Thus, a single sweepscan of the pen across the paper can print a swath of tens of thousandsof dots. The paper is stepped to permit a series of contiguous swaths.Complex digital dot matrix manipulation is used to form alphanumericcharacters, graphical images, and even photographic reproductions fromthe ink drops.

In the state of the art, the nominal printhead-to-paper spacing is aboutone millimeter. Printer designers attempt to reduce pen-to-paper spacingas a means of improving print quality. However, carriage assemblytorsional deflections can cause each printhead face, or “nozzle plate,”to be off-kilter, limiting the attempt to narrow the gap between theprinthead and the paper. As illustrated in FIG. 2, a pitch angle of theprinthead relative to the plane of the paper in the printing zone isreferred to as theta-x (θx), a roll angle is referred to as theta-y(θy), and printhead yaw is referred to as theta-z (θz). Any static ordynamic deflections during printing operations can result in dotplacement errors and undesirable artifacts in the print.

Moreover, the problem becomes more complex when more pens are added tothe printer design to accommodate higher print quality demands such asfor very high resolution photographic reproductions where the ink-jetprint is indistinguishable from a photolab darkroom developer processphotograph, or multi-printhead, staggered, printhead array carriages forimproving throughput. The larger the pen carriage, the greater theproblem.

Most attempts to solve the problem focus on creating a more stable baseplatform for the hard copy apparatus as a whole. Such solutions oftenresult in the use of heavier, more expensive, manufacturing materials ordesigns having a larger work space footprint.

Moreover, manufacturing tolerances allowed in springs, pen body datums,and the like parts of the assembly, can result in variations intorsional deflections in the carriage from assembly-to-assembly. Thus,another solution is required.

Other methods and apparatus are designed to stabilize the printheadalignment focus on the pen-to-bay interface mechanisms; see e.g., U.S.patent application Ser. No. 08/878,489 by common assignee Williams, etal. for an INKJET PEN ALIGNMENT MECHANISM AND METHOD, or U.S. patentapplication U.S. Ser. No. 09/431,712 by common assignor Williams, et al.for a DATUM STRUCTURE FOR COMPACT PRINT CARTRIDGE, or U.S. patentapplication Ser. No. 09/431,711 by Heiles et al. for a UNITARY LATCHINGDEVICE FOR SECURE POSITIONING OF PRINT CARTRIDGE(S) DURING PRINTING,PRIMING AND REPLENISHMENT (each assigned to the common assignee hereinand incorporated herein by reference).

Therefore, there is a need for simplified mechanisms to reduce torsionaldeflections in ink-jet printhead carriage assemblies.

SUMMARY OF THE INVENTION

In its basic aspects, the present invention provides an ink-jet writinginstrument carriage assembly for an ink-jet printer having a printingaxis, a print media transport axis, and an ink drop firing axis,including: a carriage; a movable pen latch; a pen latch handleassociated with the pen latch; and a biased handle retainer associatedwith the carriage, wherein the carriage and pen latch are each providedwith complementary interfit devices such that when the movable pen latchis in a closed position with the retainer interlocked with the handle,the carriage and latch are held by the interfit devices with zeroclearance interfit in at least one the axis such that torsionaldeflections of the carriage are thereby reduced.

In another basic aspect, the present invention provides an ink-jetwriting instrument carriage assembly, including: a carriage for mountingat least one ink-jet printhead and for scanning across print mediumpositioned adjacently thereto such that the printhead is positioned withan ink drop nozzle side aligned for depositing ink drops on the printmedium and a holddown side aligned for receiving a latching force;movable pen latch mechanisms for accessing the printhead mounted in thecarriage when the latch mechanism is in an open position and forproviding a force against a holddown side of the printhead when in aclosed position; fixedly mounted to the carriage, latch retainermechanisms for receiving the pen latch mechanisms via complementaryinterfit devices of each; mounted on the pen latch mechanisms, latchhandle mechanisms for securing the pen latch mechanisms against thecarriage and forcing a interfit between the complementary interfitdevice; and mounted on the carriage, biased handle retainer mechanismsfor holding the latch handle mechanisms in the closed position, whereinthe carriage and pen latch mechanisms complementary interfit devicesprovide pen pitch, pen roll and pen yaw counterforces when the pen latchmechanisms is in the closed position.

In another basic aspect, the present invention provides a method forreducing torsional deflections in an ink-jet writing-instrumentcarriage. The method includes the steps of: providing the carriage andwriting-instrument latch with geometrically configured complementaryinterfit surfaces; and positioning the writing-instrument latch on thecarriage against a bias such that when the writing-instrument latch isclosed, counterforces to carriage torsional deflections which wouldaffect the printhead-to-paper orientation and distance are establishedby the complementary interfit surfaces.

In another basic aspect, the present invention provides an ink-jet hardcopy apparatus having a plurality of ink-jet writing-instruments forejecting droplets of ink in a printing zone of the apparatus, theapparatus being defined by a scanning axis, a print media transportaxis, and an ink drop firing axis, wherein the axes are mutuallyorthogonal, including: a writing-instrument carriage, mounted in theapparatus for selectively scanning the printing zone along parallel tothe scanning axis, the carriage including a plurality of bays forlocating the writing-instruments with respect to the printing zone; amovable writing-instrument latch having an open position for accessingthe bays and a closed position for securing the writing-instruments inthe bays; a writing-instrument latch handle associated with thewriting-instrument latch; and a biased handle retainer associated withthe carriage, wherein the carriage and writing-instrument latch are eachprovided with complementary interfit devices such that when the movablewriting-instrument latch is in the closed position with the retainerinterlocked with the handle, the carriage and latch are held by theinterfit devices with zero clearance interfit in at least one the axissuch that torsional deflections of the carriage are thereby reduced.

Some of the advantage of the present invention are:

it reduces torsional deflections of a scanning ink-jet printheadcarriage without resorting to heavier, more expensive manufacturingmaterials;

it is adaptable to a variety of implementations, including smallerfootprint hard copy apparatus designs;

it provides a low cost manufacturing solution;

it provides a scalable design; and

it can reduce torsional deflections of the assembly by approximately anorder of magnitude.

The foregoing summary and list of advantages is not intended by theinventors to be an inclusive list of all the aspects, objects,advantages and features of the present invention nor should anylimitation on the scope of the invention be implied therefrom. ThisSummary is provided in accordance with the mandate of 37 C.F.R. 1.73 andM.P.E.P. 608.01(d) merely to apprise the public, and more especiallythose interested in the particular art to which the invention relates,of the nature of the invention in order to be of assistance in aidingready understanding of the patent in future searches. Other objects,features and advantages of the present invention will become apparentupon consideration of the following explanation and the accompanyingdrawings, in which like reference designations represent like featuresthroughout the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (PRIOR ART) is an exemplary ink-jet printing apparatus having ascanning printhead carriage.

FIG. 2 is perspective view of an ink-jet printhead carriage assembly inaccordance with the present invention.

FIG. 2A is an exploded view of the ink-jet printhead carriage assemblyof FIG. 2 in accordance with the present invention.

FIG. 2B is a perspective view of an exemplary ink-jet printheadcartridge insertable in the carriage as shown in FIGS. 2 and 2A.

FIG. 3 is an overhead, perspective view (in partial cutaway) of acarriage component of the ink-jet printhead carriage assembly inaccordance with the present invention as shown in FIG. 2.

FIG. 4 is a side, perspective view (in partial cutaway) of a carriagecomponent of the ink-jet printhead carriage assembly in accordance withthe present invention as shown in FIGS. 2 and 3.

FIG. 5 is a perspective view of a latch component of the ink-jetprinthead carriage assembly coupled to a latch retainer component inaccordance with the present invention as shown in FIG. 2.

FIG. 6 is an illustration of close-up details of wedge controlcomponents of the ink-jet printhead carriage assembly in accordance withthe present invention as shown in FIG. 2.

FIG. 7 is an illustration of close-up details of complementary latch andlatch retainer components of the ink-jet printhead carriage assembly inaccordance with the present invention as shown in FIG. 2.

FIG. 8 is a cutaway, exploded, illustration of close-up details of latchand carriage components at the front of the ink-jet printhead carriageassembly in accordance with the present invention as shown in FIG. 2.

FIG. 9 is an example demonstrating known residual moment free bodydiagram as would be used in a deformation calculation for twist of abody.

FIGS. 9A, 9B, and 9C are schematic free body diagrams depicting theforces in operation of wedge control components of the ink-jet printheadcarriage assembly in accordance with the present invention as shown inFIG. 2.

The drawings referred to in this specification should be understood asnot being drawn to scale except if specifically noted.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference is made now in detail to a specific embodiment of the presentinvention, which illustrates the best mode presently contemplated by theinventors for practicing the invention.

FIG. 2 is an ink-jet hard copy apparatus scanning carriage assembly 200in accordance with the present invention; FIG. 2A shows an exploded viewof the same assembly. It will be recognized by those skilled in the artthat this embodiment represents one implementation and that many of thephysical features employed in a scanning carriage in order to accomplisha variety of functions are tailored to each design. As such, only thosefeatures which comprise and aid in the understanding of the presentinvention are described in detail. No limitation on the scope of theinvention is intended by the illustration of other features, nor shouldany such limitation be implied therefrom.

In this embodiment, there are five basic components of the carriageassembly 200:

(1) a pen carriage 202 (analogous to the prior art implementation ofcarriage 109 in FIG. 1),

(2) a pen latch 204,

(3) a latch retainer 206,

(4) a latch handle 208, and

(5) a handle retaining bail 210.

Shown in the pen latch 204 closed position in FIG. 2, the latch handle208 and bail 210 are configured to interact appropriately with a biasforce in any known manner such that the latch 204 is firmly seatedagainst the carriage 202. In turn, the pen latch 204 is configured inany known manner to interact with pen surfaces to firmly seat the pensin the carriage 202.

However, the interface between the pen latch 204 and the pen carriage202 uses specific features of the present invention to reducesubstantially the torsional deflections of the carriage. Laboratoryexperimentation has shown that application of the present invention canresult in a tenfold reduction of torsional deflections of a carriageassembly.

FIG. 2B depicts an exemplary printhead cartridge, or “pen,” 115Xcompatible with the eight pen bays 302 shown in FIGS. 2A and 3. Each pen115X has a shell 221 for containing an internal, ink-accumulator chamberand associated ink flow regulator devices as would be known in the art.The chamber is fluidically coupled to the internal, printhead dropgenerator mechanisms for selectively ejecting droplets of ink from thenozzles 223. A fitment 225 is provided for fluidically coupling each pen115X to an associated ink reservoirs 117X as shown in FIG. 1. A flexiblecircuit 227 has a plurality of electrical interconnects 229 for couplingeach pen 115X to the controller 102 (FIG. 1 only). Datums 231 associatedwith positioning a pen 115X in its pen bay 302 are provided as needed.

The pen carriage 202 is shown in FIGS. 3 and 4 with the pen latch 204and its handle 208 removed. This implementation of a pen carriage 202has eight pen bays 302, having appropriate pen mating features, ordatums, 303, 305, 307 and spring retainers (not shown) as needed for anyparticular pen 115X (FIGS. 1 and 2B only). Similarly, the pen contactside of the pen latch 204 is provided with appropriate mating featuresor biasing springs (not seen in these views) as may be needed to secureeach pen 115X in its associated bay 302.

The latch retainer 206 is fixedly mounted to the carriage 202 in aconventional manner, such as with fasteners (not shown) via captureholes 304 through mounting posts 306. In this embodiment, the latchretainer 206 is shown to be located approximately mid-carriage, in theupstream (i.e., toward the input paper supply) paper transit path y-axisdirection of the pen bays 302, and generally lying in an x-axis plane(i.e., relatively rearward with respect to the hard copy apparatus asdepicted in FIG. 1). The retainer 206 is provided with four (relativeleft side and right side) wedge controls 311, 312, 313, 314. The leftside outboard wedge control 311 is seen in more detail in FIG. 4 andFIG. 6; the right side outboard wedge control 313 is a mirror imageconstruct. Each retainer wedge control 311, 312, 313, 314 is generallyan open-bottomed trapezoidally-shaped receiver construct adapted forreceiving and retaining respective members of the pen latch 204, such asprotruding arm members, or tongues, 611, 612 as seen in FIG. 6 and FIG.7. Inboard wedge controls 312, 314 receive associated inboard latchtongues 612, 614 with a line-to-line fit (referred to hereinafter moresimply as “interfit”) that is generally parallel to the y-axis, whereasthe outboard wedge controls 311, 313 receive associated outboard latchtongue 611, 613 with an interfit that is generally parallel to thex-axis. As best seen in FIG. 5, the outboard wedge controls 311, 313trapezoidal constructs are open outwardly along each side of the latchretainer 206 in the x-axis and the inboard wedge controls 312, 314trapezoidal constructs are open outwardly on a side in the y-axis tofacilitate receiving the respective associated latch tongues 611, 612,613, 614.

The outboard tongues 611, 613 are each provided with a latch pivot 615(FIG. 6 only). The latch pivot 615 has a generally cylindrical orspherical outer surface 617, facing inwardly along the x-axis, forfacilitating the raising and lowering of the latch 204 to access the penbays 302. Looking particularly to FIGS. 4 and 6, the pivot 615 has aouter diameter that is greater than the span of the upper reach of thewedge control 311 (see also, FIG. 9C, described in detail hereinafter).Therefore, as the latch pivot 615 is mated with the in detailhereinafter). Therefore, as the latch pivot 615 is mated with theoutboard wedge control 311, coupling the latch 204 to the retainer 206,the outer surface 617 will contact the inside front wall 311′ and insideback wall 311″ of the wedge control before the latch pivot outer surfacereaches the inside top wall 311″′. The same fit is provided between theright side, wedge control 313 and the right side, outboard latch tongue613 (FIG. 5). Looking again to FIG. 7, the left side (bottom view)inboard tongue 612 has an x-axis, outside face 612′ that is generallyconical shaped. This outside face 612′ is configured such that it willimpact the outside inner wall 312′ of the inboard wedge control 312 whenthe latch 204 is engaged with the retainer 206 and closed onto the pens115X. The right side inboard tongue 614 is a mirror image construct.Note from FIGS. 6 and 7, that the y-axis reach of the inboard tongue 612into the inboard wedge control 312 provides a gap 619 such that there isno other interference when the latch 204 is raised and lowered duringpen bay 302 access. FIG. 5 best displays a pair of integrated latchhandle mounts 501 on a descending wall 503 of the pen latch 204. Asshown in FIG. 8 (see also FIG. 2), another set of latch front wedgecontrols 801, 802 is provided on the carriage 202 proximate the latchhandle 208 and bail 210 region of the carriage 202. The pen latch 204descending wall 503 has an edge 505, 505′ at each x-axis extremitythereof which is received against a complementary ascending wall 803 ofthe carriage 202 to form the latch front wedge controls 801, 802. Whenmated, the latch front wedge controls 801, 802 provide x-axis linearconstraint. complementary tongue-wedge control pairs, then capturing thebail 210 with the latch handle 208, and closing the latch 204 to secureink-jet pens in the bays 302, will create contact forces between thetongues 611, 612, 613, 614 and respective wedge controls 311, 312, 313,314, effectively “wedging” the fit between the latch and the retainer206. In other words, relative motion, or more specifically, distortionof the carriage assembly—except for theta-x rotations—between the latch204 and the retainer 206, which is securely fastened to the carriage, issubstantially eliminated due to the forces set up by the wedge controlcomponents .

FIG. 9 demonstrates the complexity of a large carriage which results intorsional deflections that can affect pen-to-paper alignment anddistance and result in printing errors. Let A-H represent pens in acarriage 900 mounted for translation along the axis X—X of a rod 902.Thus, $\begin{matrix}{{{\sum M_{0}} = {0 = {{\sum\limits_{n = A}^{H}( {{Fz1n}*{X1n}} )} + ( {{Fz2n}*{X2n}} ) + M_{R}}}},} & ( {{Equation}\quad 1} )\end{matrix}$

where it is known from mechanics of solids that “M_(R),” a the residualmoment born by a body—in this case the carriage torsional twist, can beexpressed as:

M _(R) =JGθ÷L  (Equation 2),

where J=section modulus, G=torsional modulus, θ=angular twist, and L isthe distance from the latch rotational axis to the bail attachmentpoint.

Thus, if the section modulus J can be increased, angular twist θ can bedecreased.

The torsional deflection restraining affects of the present invention,accomplishing the requisite decrease in angular twist θ, can now berecognized. The latch 204 is assumed for the purpose of the followingdiscussion to be closed as shown in FIGS. 2 and 8 such that a pen 115Xis firmly seated in each bay 302 (FIGS. 2A and 3) of the carriage 202.Referring also to FIG. 9A, with each conical face of the inboard latchtongues 612, 614 pressed against the outer wall of the associated latchretainer inboard wedge controls 312, 314, a constraining force, parallelto the carriage-scanning x-axis, is applied to the assembly 200 at eachtongue. The normal force “N” at control face 612′ for tongue 612 is atan angle “α” designed such that:

α<tan⁻¹ μ  (Equation 3),

where μ is the coefficient of friction for the materials employed, toavoid sliding motion along face 612″ due to applied forces, arrow “Fx,”during translation of the carriage in the x-axis. In the presentembodiment, α≈8°. A range of five to fifteen degrees is preferred but,in general, the wedge control surface angles should be chosen for aspecific design to be self-locking. Note that the top surface 612″ doesnot contact the inner upper surface 312″ of inboard wedge control 312,nor does the inboard side wall 612″′ of the tongue 612. The arrowlabeled “F_(Latch)” represents the sum of the forces created when thelatch 204 is secured to the carriage 202 via the handle 208 and bail210.

FIG. 9B schematically demonstrates representative forces in the z-axisextant when the latch 204 is closed on the pens 115X:

F_(ZLR)=forces at the latch retainer,

F_(ZLX)=forces at the latch at first extremity datums 231 (FIG. 2B) ofeach pen 115X,

F_(ZLSX)=forces at the latch spring 901 provided for each pen,

F_(Z2LX)=forces at the latch at an opposite extremity datums of the pen,and

F_(ZLH)=forces at the latch handle.

Similarly, and now referring also to FIG. 9C, with the latch pivot 615outer surface 616 pressed into the latch retainer outboard wedgecontrols 311, 313 on each side of the latch 204 (with only controlsurfaces—walls 311″ and 311″—seen in this view), constraining forces,“Fy,” parallel to the paper transport y-axis are applied to the assembly200 at each. As such, y-axis relative motion and theta-y and theta-zdeflections are opposed by the constraining forces.

As such, theta-y and theta-z carriage deflections are directly opposedby the constraining force. Similarly, the conical faces 811, 822 on thedescending wall 502 mating with the front wedge controls 801, 802 causea constraining forces parallel to the paper transport y-axis toward therelative front of the carriage. This sets up theta-y and theta-zdeflection opposition. Thus, employing the present invention, carriagetwist and deformations are substantially reduced. In other words, thecarriage-latch assembly torsional stiffness has be substantiallyincreased. As a result, pen printhead pitch, θx, printhead roll, θy, andprinthead yaw, θz, are all provided for with counter-forcesautomatically employed when the pen latch 204 is shut and locked usingthe bail 210 and latch handle 208, positioned as shown in FIGS. 2 and 8.

Thus, print quality is more free of artifacts. Therefore, the presentinvention provides a carriage for an ink-jet printer constrainstorsional deflections by providing carriage to pen latch interfacefeatures having a zero clearance interfit such that when opened, the penlatch allows individual pens to be accessed and when closed the penlatch reduces the carriage torsional deflections and increasing thetorsional stiffness of the assembly by providing biasing forces at eachthe interface feature. Stated more generally, by providing the carriageand pen latch with geometrically configured complementary interfitsurfaces wherein when the pen latch is closed, counterforces to carriagetorsional deflections which would affect the printhead-to-paperorientation are established.

The foregoing description of the preferred embodiment of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form or to exemplary embodiments disclosed.Obviously, many modifications and variations will be apparent topractitioners skilled in this art. For example, other geometric specificshapes and orientations for the wedge control constructs can be designedfor a specific carriage. The invention is not limited to scanningcarriages; page-wide and page-size ink-jet printhead carriages areadaptable to the present invention. Moreover, while no pen bay side biaselements, such as springs, have been shown, it will be recognized bythose skilled in the art, that they can be employed as needed.Similarly, any process steps described might be interchangeable withother steps in order to achieve the same result. The embodiment waschosen and described in order to best explain the principles of theinvention and its best mode practical application, thereby to enableothers skilled in the art to understand the invention for variousembodiments and with various modifications as are suited to theparticular use or implementation contemplated. It is intended that thescope of the invention be defined by the claims appended hereto andtheir equivalents. Reference to an element in the singular is notintended to mean “one and only one” unless explicitly so stated, butrather means “one or more.” Moreover, no element, component, nor methodstep in the present disclosure is intended to be dedicated to the publicregardless of whether the element, component, or method step isexplicitly recited in the following claims. No claim element herein isto be construed under the provisions of 35 U.S.C. Sec. 112, sixthparagraph, unless the element is expressly recited using the phrase“means for . . . ”

What is claimed is:
 1. An ink-jet pen carriage assembly for an ink-jetprinter having a printing axis constituting a x-axis, a print mediatransport axis constituting a y-axis, and an ink drop firing axisconstituting a z-axis, the assembly comprising: a carriage; a movablepen latch having an open position and a closed position; a positioningmechanism associated with the movable pen latch; and a positioningmechanism retainer associated with the carriage, wherein the carriageand the movable pen latch are each provided with complementary interfitdevices such that when the movable pen latch is in a closed position,the carriage and the movable pen latch are held by the interfit deviceswith zero clearance interfit in at least one axis selected from saidx-axis, y-axis, and z-axis such that torsional deflections of thecarriage are reduced, and wherein the interfit devices include at leastone pen latch retainer on the carriage and each pen latch retainerincludes wedge-configured receivers having receiver mating surfaces forproviding y-axis constraint, and a protruding arm on the pen latch, thearm including a pivot having a surface wherein the pivot is interfitagainst the mating surfaces such that the movable pen latch can berotated between the open position and the closed position and theinterfit provides y-axis, z-axis, theta-y and theta-z constraints foreach pen.
 2. The assembly as set forth in claim 1, comprising: aplurality of said complementary interfit devices are provided anddisbursed in the y-axis for holding the carriage and the latch with zeroclearance interfit in at least two axes selected from said x-axis, saidy-axis, and said z-axis.
 3. The assembly as set forth in claim 1,comprising: the interfit devices setting up counterforces to pen yawtorsional deflection tendencies of the carriage when the pen latch is inthe closed position.
 4. The assembly as set forth in claim 1,comprising: the interfit devices setting up counterforces to pen rolltorsional deflection tendencies of the carriage when the pen latch is inthe closed position.
 5. The assembly as set forth in claim 1,comprising: the interfit devices setting up counterforces to pen pitchtorsional deflection tendencies of the carriage when the pen latch is inthe closed position.
 6. The assembly as set forth in claim 1,comprising: each pen latch retainer including wedge-configured receivershaving receiver mating surfaces for providing x-axis constraint, and thearm including at least one face having a geometric configuration forestablishing an interfit against at least one of the receiver matingsurfaces such that in the closed position the interfit provides x-axisand z-axis constraints for each pen.
 7. The assembly as set forth inclaim 6, comprising: the mating surfaces are provided with surfaceangles wherein the contact between the surfaces forms an interlock. 8.The assembly as set forth in claim 1, further comprising: a handle and ahandle retainer for biasing the handle into a locked position when thepen latch is in the closed position; and the interfit devices include atleast one wedge-configured receiver positioned on the carriage in aregion proximate the retainer, the receiver having a mating surface forproviding y-axis constraint, and the pen latch having at least onesurface having a face having a geometric configuration for establishingan interfit against the mating surface when the pen latch is in theclosed position such that the interfit provides y-axis, z-axis, theta-x,and theta-z constraints of each pen.
 9. The assembly as set forth inclaim 1, comprising: the complementary interfit devices provide penpitch, pen roll and pen yaw counterforces when the movable pen latch isin the closed position.
 10. An ink-jet writing instrument carriageassembly, comprising: carriage means for mounting at least one ink-jetprinthead and for scanning across print medium positioned adjacentlythereto such that the printhead is positioned having an ink drop nozzleside aligned for depositing ink drops on the print medium and a holddownside aligned for receiving a latching force; movable latch means foraccessing the printhead mounted in the carriage means when the latchmeans is in an open position and for providing the latching forceagainst the holddown side when the latch means is in a closed position;fixedly mounted to the carriage means, latch retainer means forreceiving the latch means via complementary interfit devices of each,wherein the interfit devices include a latch retainer on the carriagemeans, the retainer including wedge-configured receivers having receivermating surfaces for providing print media transport axis constraint, anda protruding arm on the latch means, the arm including a pivot having asurface wherein the pivot is interfit against the mating surfaces suchthat the latch means can be rotatably moved between the open positionand the closed position such that the interfit provides print mediatransport axis constraint, ink drop firing axis constraint, printheadroll constraint, and printhead yaw constraint for said printhead;associated with the latch means, latch securing means for securing thelatch means against the carriage means and forcing an interfit betweenthe interfit devices; and mounted on the carriage means, bias means forholding the latch securing means with the latch means in the closedposition, wherein the interfit devices provide printhead pitch, roll andyaw counterforces when the latch means is in the closed position andwherein a plurality of the interfit devices are provided, mounted in adisplaced configuration in the print media transport axis for holdingthe carriage means and the latch means with a zero clearance interfit inat least two axes selected from a printhead axis, the print mediatransport axis, and the ink drop firing axis.
 11. The assembly as setforth in claim 10, comprising: the interfit devices setting upcounterforces to yaw torsional deflection tendencies of the carriagemeans when the latch means is in the closed position.
 12. The assemblyas set forth in claim 10, comprising: the interfit devices setting upcounterforces to roll torsional deflection tendencies of the carriagemeans when the latch means is in the closed position.
 13. The assemblyas set forth in claim 12, comprising: the interfit devices setting upcounterforces to pitch torsional deflection tendencies of the carriagemeans when the latch means is in the closed position.
 14. The assemblyas set forth in claim 10, comprising: the interfit devices include alatch retainer on the carriage means, the retainer includingwedge-configured receivers having receiver mating surfaces for providingprinthead scanning axis constraint, and a protruding arm on the latchmeans, the arm including at least one face having a geometricconfiguration for establishing a interfit against at least one of thereceiver mating surfaces such that in the closed position, the interfitprovides printhead scanning axis and printhead ink drop firing axisconstraints.
 15. The assembly as set forth in claim 14, comprising: themating surfaces are provided with surface angles wherein the contactbetween the surfaces forms an interlock.
 16. The assembly as set forthin claim 10, comprising: the interfit devices include at least onewedge-configured receiver positioned on the carriage means in a regionproximate the bias means, the receiver having a mating surface forproviding print media transport axis constraint, and the latch meanshaving at least one surface having a face having a geometricconfiguration for establishing a interfit against the mating surfacewhen the latch means is in the closed position such that the interfitprovides print media transport axis constraint, printhead ink dropfiring axis constraint, printhead pitch constraint, and printhead yawconstraint.
 17. The assembly as set forth in claim 10, comprising: thecomplementary interfit devices provide pitch, roll and yaw counterforceswhen the latch means is in the closed position.
 18. An ink-jet hard copyapparatus having a plurality of ink-jet writing-instruments, each havingat least one printhead for ejecting droplets of ink in a printing zoneof the apparatus, the apparatus being defined by a scanning x-axis, aprint media transport y-axis, and an ink drop firing z-axis, wherein theaxes are mutually orthogonal, the apparatus comprising: awriting-instrument carriage, mounted in the apparatus for selectivelyscanning the printing zone substantially parallel to the x-axis, thecarriage including a plurality of bays for mounting thewriting-instruments with respect to the printing zone; a movablewriting-instrument latch having an open position for accessing the baysand a closed position for securing the writing-instruments in the bays;a writing-instrument latch handle associated with the writing-instrumentlatch; and a biased handle retainer associated with the carriage,wherein the carriage and the latch are each provided with complementaryinterfit devices such that when the latch is in the closed position withthe retainer interlocked with the handle, the carriage and latch areheld by the interfit devices with zero clearance interfit in at leastone of the axes such that torsional deflections of the carriage arethereby reduced and wherein the interfit devices include a latchretainer on the carriage,the latch retainer including wedge-configuredreceivers having receiver mating surfaces for providing y-axisconstraint, and a protruding arm on the latch, the arm including a pivothaving a surface wherein the pivot is interfit against the matingsurfaces such that the latch can be rotatably moved between the openposition and the closed position and the interfit devices provide y-axisconstraint, z-axis constraint, theta-y constraint and theta-zconstraint.
 19. The assembly as set forth in claim 18, comprising: aplurality of the interfit devices are provided and displaced in they-axis for holding the carriage and the latch with zero clearanceinterfit in at least two axes.
 20. The assembly as set forth in claim18, comprising: the interfit devices setting up counterforces to yawtorsional deflection tendencies of the carriage when the latch is in theclosed position.
 21. The assembly as set forth in claim 18, comprising:the interfit devices setting up counterforces to roll torsionaldeflection tendencies of the carriage when the latch is in the closedposition.
 22. The assembly as set forth in claim 18, comprising: theinterfit devices setting up counterforces to pitch torsional deflectiontendencies of the carriage when the latch is in the closed position. 23.The assembly as set forth in claim 18, comprising: the latch retainerincluding wedge-configured receivers having receiver mating surfaces forproviding x-axis constraint, and the arm including at least one facehaving a geometric configuration for establishing an interfit against atleast one of the receiver mating surfaces such that in the closedposition, the interfit provides x-axis and z-axis constraints.
 24. Theassembly as set forth in claim 23, comprising: the complementaryinterfit devices are provided with surface angles wherein the contactbetween the mating surfaces forms an interlock.
 25. The assembly as setforth in claim 18, comprising: the interfit devices include at least onewedge-configured front receiver positioned on the carriage in a regionproximate the biased handle retainer, the front receiver having a frontretainer mating surface for providing y-axis constraint, and the latchhaving at least one surface having a face having a geometricconfiguration for establishing an interfit against the front retainermating surface when the latch is in the closed position such that theinterfit provides y-axis, z-axis, theta-x, and theta-z constraints. 26.The assembly as set forth in claim 18, comprising: the carriage andlatch complementary interfit devices provide writing-instrument pitch,roll and yaw counterforces when the latch is in the closed position. 27.An ink-jet pen carriage assembly for an ink-jet printer having aprinting axis constituting a x-axis, a print media transport axisconstituting a y-axis, and an ink drop firing axis constituting az-axis, comprising: a carriage; a movable pen latch having an openposition and a closed position; positioning mechanisms associated withthe movable pen latch; and a positioning mechanism retainer associatedwith the carriage, wherein the carriage and the movable pen latch areeach provided with complementary interfit devices such that when themovable pen latch is in the closed position, the carriage and themovable pen latch are held by the interfit devices with zero clearanceinterfit in at least one axis selected from said x-axis, said y-axis,and said z-axis, such that torsional deflections of the carriage arereduced, the retainer including wedge-configured receivers havingreceiver mating surfaces for providing x-axis constraint, and aprotruding arm on the movable pen latch, the arm including at least oneface having a geometric configuration for establishing an interfitagainst at least one of the receiver mating surfaces such that in theclosed position, the interfit provides x-axis and z-axis constraints foreach pen.
 28. The assembly as set forth in claim 27, further comprising:a handle and a handle retainer for biasing the handle into a lockedposition when the pen latch is in the closed position; and the interfitdevices include at least one wedge-configured receiver positioned on thecarriage in a region proximate the retainer, the receiver having amating surface for providing y-axis constraint, and the pen latch havingat least one surface having a face having a geometric configuration forestablishing an interfit against the mating surface when the pen latchis in the closed position such that the interfit provides y-axis,z-axis, theta-x, and theta-z constraints of the pens.
 29. The assemblyas set forth in claim 27, comprising: the interfit devices provide penpitch, pen roll and pen yaw counterforces when the movable pen latch isin the closed position.
 30. The assembly as set forth in claim 27,comprising: the mating surfaces are provided with surface angles whereinthe contact between the surfaces forms an interlock.
 31. An ink-jet pencarriage assembly for an ink-jet printer having a printing axisconstituting an x-axis, a print media transport axis constituting ay-axis, and an ink drop firing axis constituting a z-axis, comprising: acarriage; a movable pen latch having an open position and a closedposition; a positioning mechanism associated with the movable pen latch;a positioning mechanism retainer associated with the carriage, whereinthe positioning mechanism retainer and the movable pen latch are eachprovided with complementary interfit devices such that when the movablepen latch is in a closed position, the carriage and the movable penlatch are held by the interfit devices with zero clearance interfit inat least one axis selected from said x-axis, said y-axis, and saidz-axis, such that torsional deflections of the carriage are reduced; anda handle and a handle retainer for biasing the handle into a lockedposition when the pen latch is in the closed position, and wherein theinterfit devices also include at least one wedge-configured receiverpositioned on the carriage in a region proximate the handle retainer,the receiver having a mating surface for providing y-axis constraint,and the pen latch having at least one surface having a face having ageometric configuration for establishing an interfit against the matingsurface when the pen latch is in the closed position such that theinterfit provides y-axis, z-axis, theta-x, and theta-z constraints ofeach pen.
 32. The assembly as set forth in claim 31, comprising: thepositioning mechanism retainer including positioning mechanismwedge-configured receivers having positioning mechanism mating surfacesfor providing y-axis constraint, and the interfit devices furtherincluding a protruding arm on the pen latch, the arm including a pivothaving a pivot surface wherein the pivot is interfit against thepositioning mechanism mating surfaces such that the pen latch can berotatably moved between the open position and the closed position andthe interfit provides y-axis, z-axis, theta-y and theta-z constraints.33. The assembly as set forth in claim 31, comprising: each pen latchretainer including wedge-configured receivers having receiver matingsurfaces for providing x-axis constraint, and the interfit devicesfurther including a protruding arm on the movable pen latch, the armincluding at least one face having a geometric configuration forestablishing an interfit against at least one of the positioningmechanism receiver mating surfaces such that in the closed position, theinterfit provides x-axis and z-axis constraints.
 34. An ink-jet writinginstrument carriage assembly, comprising: a carriage mount for at leastone ink-jet printhead for scanning across print medium positionedadjacently thereto such that the printhead is positioned having an inkdrop nozzle side aligned for depositing ink drops on the print mediumand a holddown side aligned for receiving a latching force; a movableprinthead latch accessing the printhead mounted in the carriage mountwhen the latch is in an open position and providing the force againstthe holddown side when the latch is in a closed position; fixedlymounted to the carriage mount, a latch retainer for receiving the latchvia complementary interfit devices of each, the interfit devicesincluding a printhead latch retainer on the carriage mount, the retainerincluding wedge-configured receivers having receiver mating surfaces forproviding x-axis constraint, and a protruding arm on the printheadlatch, the arm including at least one face having a geometricconfiguration for establishing an interfit against at least one of thereceiver mating surfaces such that in the closed position the interfitprovides printhead alignment x-axis and ink drop firing z-axisconstraints for the printhead; and associated with the latch andcarriage mount, a latch holder for holding the latch against thecarriage mount and forcing the interfit between the complementaryinterfit devices with the latch in the closed position, wherein theinterfit devices provide printhead pitch, printhead roll and printheadyaw counterforces when the printhead latch is in the closed position andwherein a plurality of the complementary interfit devices are providedand displaced in a print medium transport y-axis for holding thecarriage mount and the latch with zero clearance interfit in at leasttwo axes selected from the x-axis, y-axis and z-axis.
 35. The assemblyas set forth in claim 34, comprising: the latch retainer includingwedge-configured receivers having receiver mating surfaces for providingy-axis constraint, and the interfit devices including a protruding armon the latch, the arm including a pivot having a surface wherein thepivot is interfit against the receiver mating surfaces such that thelatch can be rotatably moved between an open position and the closedposition and the interfit provides y-axis, z-axis, theta-y and theta-zconstraints.
 36. The assembly as set forth in claim 34, comprising: theinterfit devices include at least one wedge-configured front receiverpositioned on the carriage mount in a region proximate the latch holder,the front receiver having a front mating surface for providing y-axisconstraint, and the latch having at least one surface having a facehaving a geometric configuration for establishing an interfit againstthe front mating surface when the latch is in the closed position suchthat the interfit provides y-axis, z-axis, theta-x, and theta-zconstraints.
 37. The assembly as set forth in claim 34, comprising: thecomplementary interfit devices provide pitch, roll and yaw counterforceswhen the latch is in the closed position.
 38. The assembly as set forthin claim 34, comprising: the mating surfaces are provided with surfaceangles wherein the contact between the mating surfaces forms aninterlock.
 39. An ink-jet writing instrument carriage assembly,comprising: carriage mount for at least one ink-jet printhead such thatthe printhead is positioned having an ink drop nozzle side aligned fordepositing ink drops on the print medium and a holddown side aligned forreceiving a latching force; a movable latch for accessing the printheadmounted in the carriage mount when the latch is in an open position andfor providing the latching force against the holddown side when thelatch is in a closed position; fixedly mounted to the carriage mount, alatch retainer for receiving the latch via complementary interfitdevices of each, wherein the interfit devices include at least onewedge-configured receiver positioned on the carriage mount, the receiverhaving a mating surface for providing print media transport axisconstraint, and the latch having at least one surface having a facehaving a geometric configuration for establishing an interfit againstthe mating surface when the pen latch is in the closed position suchthat the interfit provides print media transport y-axis constraint,ink-drop firing z-axis constraint, printhead pitch constraint, andprinthead yaw constraint; and associated with the latch and the carriagemount, a latch holder, having a bias, for securing the latch against thecarriage mount and forcing the interfit between the complementaryinterfit devices, wherein the carriage mount and latch complementaryinterfit devices provide printhead pitch, printhead roll and printheadyaw counterforces when the latch is in the closed position and wherein aplurality of the complementary interfit devices are provided anddisbursed in the y-axis for holding the carriage mount and the latchwith zero clearance interfit in at least two axes.
 40. The assembly asset forth in claim 39, comprising: the retainer includingwedge-configured receivers having receiver mating surfaces for providingy-axis constraint, and the interfit devices including a protruding armon the latch, the arm including a pivot having a surface wherein thepivot is interfit against the mating surfaces such that the latch can berotatably moved between an open position and the closed position and theinterfit provides y-axis, z-axis, theta-y and theta-z constraints. 41.The assembly as set forth in claim 39, comprising: the interfit devicesincludes at least one wedge-configured holder receiver positioned on thecarriage mount in a region proximate the bias, the holder receiverhaving a holder mating surface for providing y-axis constraint, and thelatch having at least one surface having a face having a geometricconfiguration for establishing a interfit against the holder matingsurface when the latch is in the closed position such that the interfitprovides y-axis, z-axis, theta-x, and theta-z constraints.
 42. Theassembly as set forth in claim 39, comprising: the complementaryinterfit devices provide pitch, roll and yaw counterforces when thelatch is in the closed position.
 43. The assembly as set forth in claim39, comprising: the mating surfaces are provided with surface angleswherein the contact between the surfaces forms an interlock.
 44. Anink-jet hard copy apparatus having a plurality of ink-jetwriting-instruments, each having at least one printhead for ejectingdroplets of ink in a printing zone of the apparatus, the apparatus beingdefined by a print receiving x-axis, a print media transport y-axis, andan ink drop firing z-axis, wherein the axes are mutually orthogonal,comprising: a writing-instrument carriage, mounted in the apparatusadjacent the printing zone, the carriage including a plurality of baysfor mounting the writing-instruments with respect to the printing zone;a movable writing-instrument latch having an open position for accessingthe bays and a closed position for securing the writing-instruments inthe bays; a writing-instrument latch handle associated with thewriting-instrument latch; and a biased handle retainer associated withthe carriage, wherein the carriage and the latch are each provided withcomplementary interfit devices such that when the latch is in the closedposition with the retainer interlocked with the handle, the carriage andlatch are held by the interfit devices with zero clearance interfit inat least one of the axes such that torsional deflections of the carriageare thereby reduced, and wherein the interfit devices include a latchretainer on the carriage, the latch retainer including wedge-configuredreceivers having receiver mating surfaces for providing x-axisconstraint, and a protruding arm on the latch, the arm including atleast one face having a geometric configuration for establishing ainterfit against at least one of the receiver mating surfaces such thatin the closed position, the interfit provides x-axis and z-axisconstraints.
 45. The assembly as set forth in claim 44, comprising: thelatch retainer including wedge-configured receivers having receivermating surfaces for providing y-axis constraint, the arm including apivot having a surface wherein the pivot is interfit against thereceiver mating surfaces such that the latch can be rotatably movedbetween an open position and the closed position and the interfitprovides y-axis, z-axis, theta-y and theta-z constraints.
 46. Theassembly as set forth in claim 44, comprising: the interfit devicesinclude at least one wedge-configured front receiver positioned on thecarriage in a region proximate the biased handle retainer, the frontreceiver having a front receiver mating surface for providing y-axisconstraint, and the latch having at least one surface having a facehaving a geometric configuration for establishing a interfit against thefront receiver mating surface when the latch is in the closed positionsuch that the interfit provides y-axis, z-axis, theta-x, and theta-zconstraints.
 47. The assembly as set forth in claim 44, comprising: theinterfit devices provide pitch, roll and yaw counterforces when thelatch is in the closed position.
 48. The assembly as set forth in claim44, comprising: the interfit devices are provided with surface angleswherein the contact between the mating surfaces forms an interlock. 49.An ink-jet hard copy apparatus having a plurality of ink-jetwriting-instruments, each having at least one printhead for ejectingdroplets of ink in a printing zone of the apparatus, the apparatus beingdefined by a print receiving x-axis, a print media transport y-axis, andan ink drop firing z-axis, wherein the axes are mutually orthogonal,comprising: a writing-instrument carriage, mounted in the apparatusadjacent the printing zone, the carriage including a plurality of baysfor mounting the writing-instruments with respect to the printing zone;a movable writing-instrument latch having an open position for accessingthe bays and a closed position for securing the writing-instruments inthe bays; a writing-instrument latch handle associated with thewriting-instrument latch; and a biased handle retainer associated withthe carriage, wherein the carriage and the latch are each provided withcomplementary interfit devices such that when the latch is in the closedposition with the handle retainer interlocked with the handle, thecarriage and latch are held by the interfit devices with zero clearanceinterfit in at least one of the axes such that torsional deflections ofthe carriage are thereby reduced, and wherein the interfit devicesincludes at least one wedge-configured receiver positioned on thecarriage in a region proximate the biased handle retainer, the receiverhaving a mating surface for providing y-axis constraint, and the latchhaving at least one surface having a face having a geometricconfiguration for establishing an interfit against the mating surfacewhen the latch is in the closed position such that the interfit providesy-axis, z-axis, theta-x, and theta-z constraints.
 50. The assembly asset forth in claim 49, comprising: the interfit devices include a penlatch retainer on the carriage, the retainer including firstwedge-configured receivers having first receiver mating surfaces forproviding y-axis constraint, and a protruding arm on the latch, the armincluding a pivot having a surface wherein the pivot is interfit againstthe mating surfaces such that the latch can be rotatably moved betweenan open position and the closed position and the interfit providesy-axis, z-axis, theta-y and theta-z constraints for each printhead. 51.The assembly as set forth in claim 49, comprising: the interfit devicesincludes a latch retainer on the carriage, the latch retainer includingsecond wedge-configured receivers having second receiver mating surfacesfor providing x-axis constraint, and the arm including at least one facehaving a geometric configuration for establishing an interfit against atleast one of the second receiver mating surfaces such that in the closedposition the interfit provides x-axis and z-axis constraints.
 52. Theassembly as set forth in claim 49, comprising: the carriage and latchcomplementary interfit devices provide writing-instrument pitch, rolland yaw counterforces when the latch is in the closed position.
 53. Theassembly as set forth in claim 49, comprising: the interfit devices areprovided with surface angles wherein the contact between the matingsurfaces forms an interlock.